<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .box{
        width: 300px;
        height: 100px;
        /* border: 1px solid #111; */
    }
    #box1{
        width: 250px;
        height: 50px;
        background-color: blanchedalmond;
        border: 1px solid #ffefa4;
        font-size: 14px;
        display: none;
        /* display: block */
    }
</style>
<body>
    <div class="box" onmouseover="ys()" onmouseout="yc()"><p><input type="checkbox">两周内自动登录</p>
        <div id="box1">为了您的信息安全,请不要在网吧或公用电脑上使用此功能！</div>
    </div> 
    
</body>
<script>
    function ys(){
        var x=document.getElementById('box1').style.display='block'
    }
    function yc(){
        var x=document.getElementById('box1').style.display='none'
    }
</script>
</html>